Helicopter portable drill rigs have been developed for use in remote locations where it is difficult to transport and locate more conventional earth drilling equipment. Examples of such helicopter portable drill rigs are (1) a drill rig marketed under the name Heli-Drill by Big Indian Drilling, Company, Ltd. of Calgary, Alberta, Canada, (2) a drill rig marketed under the name Midway Copter-Rig model 13MH by Midway Manufacturing and Supply, Inc., a subsidiary of Texas International Company of Odessa, Texas, and (3) a drill rig marketed under the name Mayhew Model 50 Portable Demountable Drill by Gardner-Denver of Dallas, Texas. Prior to the present invention, however, helicopter portable drill equipment has suffered from any one or more of several disadvantages which makes them unsuitable for drilling in hard rock at high elevations such as in the Rocky Mountains. The typical disadvantages of the prior art helicopter portable drill rigs are that they are so heavy that they require relatively large and expensive helicopter transportation making the drilling operation unduly expensive and they do not operate efficiently in the thin air prevelent at high altitudes.
The lack of a portable drill rig capable of operating efficiently at high altitudes is understandable since to design such a drill rig requires the blending of component parts which are capable of operating in thin air and yet which are light enough that they can be transported by smaller, relatively inexpensive helicopters.
The need for helicopter portable drill rigs which will operate at high altitudes has increased within the last decade due to the diminishing supply of petroleum products necessitating the search for these products in more remote areas, some of which are at high altitutes. The search for petroleum products frequently involves seismic exploration work prior to the drilling of an exploratory well with the seismic work typically being conducted with the use of dynamite explosions that set off sound waves through the earth's crust which are recorded by specially designed equipment to give the exploration company a better picture of the subsurface rock formation. For environmental reasons, it is desirable to set the explosive charge below the surface of the earth but this requires drilling shallow holes into which the dynamite charge can be placed and prior to the present invention economical portable drilling equipment suitable for drilling in hard rock at high elevations, such as in the Rocky Mountains, has not been available.